Less than four months after 20 children and six adults were killed in the Sandy Hook Elementary School shooting in Newtown, Conn, Glee tackled the sensitive subject by beginning with a disclaimer. "This episode of Glee addresses the topic of school violence," the show warned. "Viewer discretion is advised."

In the emotional episode, two shots were heard inside McKinley High School as the glee club practiced inside the choir room. Teacher Will Schuester (Matthew Morrison) and Coach Beiste (Dot Jones) quickly instructed the students to hide in the room. "Start texting, tweeting, let everyone know what's going on but don't tell them we're here. Alright?" Scheuster told his class. "Shooters have smart moves, too."

Fearing the worst, the teens tearfully texted and video messaged their families and loved ones -- and worried about Brittany (Heather Morris), who was hiding from the suspected shooter in the bathroom. (Schuester eventually retrieved Brittany, bringing her back to relative safety.)

After a SWAT team gave the all-clear sign and began investigating the shooting, the class gathered for a group hug, but were still very shaken.

At the end of the episode, it was revealed that the gun was accidentally fired by Becky Jackson (Lauren Potter), a student with Down syndrome. "I was scared, coach, about graduating, being out in the world. With no one to protect me," she told cheerleading coach Sue Sylvester (Jane Lynch), showing her the revolver -- her father's -- that she'd brought to school. "I wanted to be prepared and protect myself. I need help." After Coach Sylvester convinced Becky to hand the gun over, it accidentally went off, firing twice at the floor.

Instead of turning Becky in, however, Sue turned herself into the principal -- claiming that the firearm was hers, and that it accidentally went off. Principal Figgins (Iqbal Theba) then immediately fired her.